A BITTER stand off which has left two Irish Ferries stuck in Welsh ports for four days escalated last night with more sailings under threat.

Angry seamen have barricaded themselves aboard the 51,000-tonne Ulysses, at Holyhead, and the Isle of Inishmore, which is unable to leave its berth at Pembroke Dock.

They are protesting over the company's controversial plans to replace staff with cheaper foreign workers, many from eastern Europe.

Sailors seized control of the ships on Thursday when they discovered security personnel had been sent aboard to "oversee" visits by new staff.

As the crisis deepened, port work-ers at Rosslare last night refused to allow Irish Ferries MV Normandy, carrying 113 passengers and dozens of lorries from Cherbourg, to dock

A spokesman for the company said it was likely to travel instead to Dublin, arriving at the capital's port late last night.

The spokesman said he hoped Irish Ferries would not have the same problem with staff at Dublin port, where the company had its own berth.

Fifteen crew members are believed to be "locked" inside the engine room of the Ulysses.

Hundreds of motorists and truck-ers, held up by the dispute, eventually managed to sail on services from Holyhead operated by rivals Stena.

But even Stena's operations have run into trouble with the fast ferry from the Anglesey port out of action because of "technical" problems until Wednesday morning.

The dispute, which is the second to hit the Irish company in less than a year, is due to go to Ireland's Labour Relations Commission tomorrow.

Irish Taoiseach Bertie Ahern has criticised Irish Ferries' handling of the row, but the company said it had to bring in overseas staff in order to remain competitive.

Irish Ferries said the workers from overseas, who will be on half the wages of current staff, were on familiarisation visits and the security personnel were there to ensure the continued access of company staff and port officials.

Spokesman Alf McGrath said: "The security measures were necessary because in December of last year Siptu (Services, Industrial, Professional and Technical Union) staged two strikes, and totally locked up the ship in Holyhead and would not allow regulatory agencies or any management on to the ship.

"So we have a duty and responsibility to protect our assets."

He added: "There are no plans for formal talks between the management and workforce, but managers are represented on both ferries and so there is the possibility of dialogue."

The Seamen's Union of Ireland has hit out at the company which wants to replace crew who are taking voluntary redundancy as part of a major cost cutting exercise.

A 10-day strike over foreign work-ers disrupted services from Holyhead last December.

The union's general secretary Bob Carrick said up to 90% of the crew had agreed to voluntary redundancy terms.

"The wishes of those remaining have to be respected and that's not happening," he added. "Our people were happy to sail with foreign crew on board, but not with security guards."